textblock: support escaped ' tag

while not in the official html4 spec, this was supported by all browsers
except IE during the html4 era and is now included in html5.

@fix

src/lib/evas/canvas/evas_object_textblock.c

@@ -898,6 +898,7 @@ static const char escape_strings[] =
 /* most common escaped stuff */
 ""\0"     "\x22\0"
 "&\0"      "\x26\0"
+"'\0"     "\x27\0"
 "<\0"       "\x3c\0"
 ">\0"       "\x3e\0"
 /* all the rest */